Coronal diffusion and high solar latitude recurrent energetic particle increases.

Abstract

Ulysses observations have demonstrated that energetic particle flux increases are not only found to be associated with the regularly appearing recurrent fast streams seen at mid solar latitudes but also that they persist with the same periodicity of occurrence to at least 64° latitude, well into the region where no accompanying plasma speed enhancement is obviously present. We discuss various models for this high latitude phenomenon including acceleration within a lower latitude fast stream with diffusive escape polewards in latitude or the return of flux from a region beyond Ulysses, but conclude that anisotropy data and other evidence on interplanetary diffusion coefficients support solar coronal acceleration at micro-flare sites followed by diffusion in a network of coronal paths characterised by large field magnitude gradients.